Expert’s answer: What you need to know about choosing the right ultrasonic water flow meter

Yup, there are options out there. In fact, you have a bunch of ultrasonic water flow meter options to choose from! Usually, you’re going to find two types of principles, the transit time and the Doppler principle.

The principle of transit time is not complicated. Basically, you have to have two transducers. Both contain a piezoelectric crystal and they’re both responsible for transmitting and receiving the signal. That way, they change the statement.

Ultrasonic water flow meter
Courtesy of Emerson Automation Solutions

Usually, the transducers will operate in the 1 -2 MHZ frequencies, the principle is based on the difference of time to an ultrasonic signal transmitted from the transducer across the pipe. It reads the receiving transducer in both directions- upstream and downstream. This time is compared.

When you don’t have flow, the time to transmit and receive the ultrasonic signal will be the same. But when you have flow, you’re going to have a difference of time to transmit and receive the signal. The disadvantage of this technology is the limitation with bubble and solids into the fluid. This condition can affect the calculation and cause an error of measurement.

The Doppler principle can use only a single sensor. This sensor has the transmitter and receiver sensor, as well as the piezoelectric crystal. The principle of work is single. Basically, the sound waves transmitted from the transducer will return with an altered frequency in which the fluid is in constant motion.

The change of frequency will be proportional to the velocity of the fluid and the transmitter will calculate the flow rate based on that information. The advantage of the Doppler principle is you can have bubble and solid in the fluid and you won’t have a problem with the flow measurement.

Want to find out more? Below you have a list of ultrasonic water flow meter on the market:

Other resources that might interest you

Non-contact brine flow measurement
Our customer wants to measure the flow rate of a brine stream. It’s a closed pipe on the discharge of a centrifugal pump. They don’t like magmeters but would consider ultrasonic if it’s not “too expensive.” I’m unsure of transit time because there may be too much junk in the water. Maybe a Doppler?

Measuring boiler blowdown water?
Our boiler blowdown water is in a critical transition between water and steam, so the water has pockets of steam with the dissolved solids. What is the best way to measure the water? Will the vortex flow meter work?

Reliable steam measurement?
What’s the best technology to measure high-pressure steam flow? I want a flow meter with high accuracy, reliability, long lifespan, and low cost if possible. Also, is there a portable instrument for measuring steam?

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